This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. This project will examine the role of activity in controlling the excitability and morphology of neurons. We have succeeded in making conditional mice in which we can, in a cell autonomous manner, silence all excitatory input to that neuron, by deleting all AMPA and NMDA receptors. These neurons can then be studied over various time intervals after silencing to examine the effects on neuronal excitability and morphology.